Radio-guiding system



Feb. 6, 1951 J. AlCARDl 2,540,414

RADIO GUIDING SYSTEM Filed July 1, 1947 2 A Transmitter B A B A B rTransmitter Modumor Phase 2 Qshifier (Tmnsmmerl Transmitter- 2 9 CarrierGenerator A ,Modulmorvk Modulatonl f 4 7 Cazf: 8 l l l er I PhaseShifter Modulator Currier Oscillator f Oscillator f2 \Genemor 5-OscilIator f 5 8 Amplifier Detector Filter 2 Filter '5 C |7 mpllfierDetector AmplifieD Detector Bil H Co u a f:r "1 7! IO I9 2| 2o(Amplifier l3 1A"! llfie DGIGCTOI' Ccm'nulaf a Filter INVEN TOR.

Patented Feb. 6, 1951 7 RiAD IQ GUIDINGIJSYSIEM -.J.o seph tAioar'di,Versailles France, assignorto Sadir Carp'entier, "Paris,,Franceiacorpom'tion o'fFrance rrAppli'cationizlulyl-l, 1947;seriai'Nn;.m5s;ss5

Societe lErancaise ire 'eGlaims; (01. 343-107) v *1 Itihasatlreanyioeenproposed to intiicatemadm- Iectricaliy a direction-"by use 'o'f- 'a-ninterference 1E1 iihtained' -by-".the-conibination oftwoeom- ;iponentfields, "emittedby' radiating systemspla'ced frat 'a'certain distance"apart "and "taking-advantage "(if the 'out=of=15hase "conditions *ofitsfieIdSat the ,point of receptioncausedrbythe difierenceintheFdu'r'ation ofithe travel of. the "waves emanating itherefrom, theseout-di-phaee .conditionsvarying ewith 'ther .direction Lin whichthereceiver is situtal ted.

c 7 Such a system ofiiridicalting'is' 'for example described inFrenh"1?atent No. 630,248, 'lodgdon iMay 2'l, 1926; Jby ""Socit 'AnonymeOndes Di'r'igg'es,=l:and .ientitle'd "LocationMethodZ 1 From another.-poirit'of (view, there are "known also idirectioziffiriiiing,systemsaccording'ito which lonemhearsJat the receiver aisound of a certainjfrequency, withcla predominating "intensity if the ilhearer is on..oneside of the directional axis, the i-soundi of another frequency'beingheard he is m the other .sidalthe two sounds 'being .heard with an equalforceiflheiisonthe axis itself.

- .The -:pr esent :invention concerns .a .direction 'ifinding method andapparatus producing at the ,gpoint of reception sounds of frequency f1.or J2 aecording tofthe relative .location of "the receiver with respectto theiiirectional axis,.and'this,;b,y

making use of iinterierencefields as'lhas bee'n indicated above;

- .The :present invention has more particularly afor objectflthe;production .of interference fields adapted tQLthe purposein dicat'sd. nI u -According to the invention, .two fields --0'f lthe same high ,.freguency, one of which is not modulated, and the other "is'modulatedaitthe same time by'the .audible frequencies f1 and fzya're transmittedf's'iinultan'eou'sly and-the "transmission w isf-produce'diini'sucha'a"zmannerlthat the respective wisercentages "ofmodul'ationgat ".the mointrofrecepti'on, 1 of .1- the: resultant.nrodulated :fi'ldrvary with tithe :direction in which is ioundzthereceiver, these -'peroentages zioftmodulation ivaryingipreferably-u-iniopposite' senses when thisdirectionzchanges.

The invention thus arrives at the desired results by operatin on thedepths of modulation of the received field, that is to say, by the same-mechanism' as th'at which is made' 'use o'f' in 'the French -'-PatentNo. $30,248 aforesaid, although the expression percentageof modulationis not express1y-'=-mentioned therein.

:sense in ipreferred ametho'd ldf 'cbri'sttmitibm "'f or 'its value,.;no accountbceing The receiver-sh0wn in Fig? 3 wcomprisesasing'le saiddrawings: I 1

Fig. 1 shows the arrangement of transmitting aerials. V

Fig. 2 shows the transmitter "'tfee'ding anese aerials. 3 Fig. 8 is a*s'chematic diagram ofia*receiver adapted to "lo'eused in thisinvention. '*Fig.-4 -a,schematic diagram of a modified receiver-adaptedtobe usedwith tliis invefftion. Fig. v 5 is a ,schematic diagram of a.rmodified form of transmitter adapted to be used with...this *invention.Accordingto a 'firs't'embodiment'fif theinvrition, twoomnidirectional"aerials A and is -.'('Fig. -1 transmit respectively, (1):anon modiilaltedifi'tilii 'Ha'accordingtotire-equation,

Ha=-" a $in=wt w be'ing "trie -value 'of' the high "frequency trans-"mitted,=t*and (2-) 'a'fi'eldHb o'f'thesame 'high frequency asA,simultaneouslymodulated '='by *th'e r'frequencies-fi 'and f2preferably withthe-suppres- 's'ion 'o'f the carrier "waves, anda'ccording to equation: 2 Hb=b [sin (wh n sin "2163f-|-"sin"(wt-(p2) Sin210%] The aerials A and B are at a distance ii from one another,dch-isdistance being-as is generally the case small with respect to thatwhich separates the "system AB "from the'receivin "station lyin in'thedirection AM'forming an angle 30 with the direction AB.

It is thus apparent-thaflunder these conditions .;the ..field. recei-vedin the direction .AM will have V ltakenrfifeaggen eral shifting commonto both waves:

the supplementaryashifting asbetweenw the waves transmitted from A andthose coming from B being set up by the supplementary path AB for thewaves coming from A. One has thus:

m being the vomm'0nhi8h frequency wave ileiith 'em itted'from'A"and B.

high frequency amplifier and detector-flu disedlow 5 {irequency a mannerthat each allows substantially only a frequency f1 or f2 to passtherethrough. The currents furnished by the low frequency amplifiers l2and Mare fed to the two coils l6 and H respectively, of the indicator l5according to already known methods of direction finding operating bymeans of two modulating frequencies.

It is possible obviously to replace the two low frequency amplifiers l2and M by a single amplifier 2| fed alternately through two filters H andI3, by the use of input commutator l9 and output commutator 20,permitting to pass, respectively the frequencies f1 and f2 as shown inFig. 4.

Obviously by the action of the detector and the low frequencyamplifiers, there is received respectively at the output of theseamplifiers: a current of a frequency ,f1 and of an amplitude equal tothe absolute value of:

k1 cos i-l-t) and a current of frequency f2 and of an amplitude equal tothe absolute value of:

the coefficient k1 being the same in these two formula.

, This results immediately from the fact that at the input of thedetector the respective percentages of modulation of the modulatedcurrents received are respectively proportional to [cos 1+6)] for f1 and[cos p2+6)] for f2 as is easily ascertained by making the vectorialadditions interpreting Formula 1 with the assumption that b isappreciably smaller than a,

axis defined by the equality of the currents issuing from the twoamplifiers is determined by the relation cos 1+5) cos (qaz-l-B) whichleads to qJ1+6+m1r=-( p2|-6) as the equation with the sign gives ofcourse no interesting result, the last equation may be written m beingthe whole number, 6 thus determined gives 0 by the relation establishedabove.

It is thus seen that x and at being known once and for all as also theratio the direction of one of the marked directions is determined by thevalue of the sum (Pl-I-(PZ and depends only on the latter so that thisdirection may be adjusted by a modification of the value of this sum,which constitutes an important advantage of the method of guidingaccording to the invention.

It is known, on the other hand, how to maintain, in a precise manner (inaddition to the fiei n liisd Wave-th le tae Pha 4 shift of the currentsof high frequency and also constant amplitudes of such currents, whichensures a permanent definition of the directional axis in space.

So long as is made sufficiently small, it will easily be seen thatFormula 2 not only gives a single suitable value for 8, but also asingle direction 0 for the marked axis.

It will be noted also that it is not necessary for the aerial B totransmit only the side bands of the modulated transmissions; it maytransmit also the corresponding carrier wave so long as its amplitude isnot greater than that of the side bands.

It should also be noted that it is not essential for the aerials used tobe omnidirectional, that is to say have a circular radiation diagram,and the fact of using directional aerials can simply modify the law ofvariation of the out-of-phase conditions as a function of the direction.This permits in particular using these aerials having a maximumtransmission in the direction of the marked axis (useful direction). 1

The setting up of the fields He. and Hb is, as can be seen, very simple(Fig. 2). The high frequency oscillaton generator I is connecteddirectly to the transmitter 2 which feeds aerial A. The generator I isconnected to the phase shifting device 3, which introduces a delay (p1into the oscillation fed therethrough to the modu later 4 which alsoreceives the frequency f1 from the oscillator 5. The highfrequency'oscillation generator I also feeds oscilations through thephase shifting device 6, that introduces the delay (p2 therein, to themodulator 1 which is also connected to receive the frequency f2 from theoscillator 8. The modulators 4 and I operate in parallel on atransmitter 9 feeding the aerial B. It is clear that this arrangementcan be submitted to many modifications.

YThe above construction leads to utilising at the point of thereception, the relative out-ofphase conditions between two similarfields He. and Hb, each having an amplitude independent of the directionof transmission.

This last condition is not however essential.

It is possible to design other constructions, as shown in Fig. 5,producing the same result and which in consequence come within thespirit of the present invention, for example the field may assume theshape corresponding to the formula:

These two fieds are obviously very easy 7 to transmit, their productionbeing common knowledge in the art. This modification is however inprinciple less advantageous than the first embodiment disclosed sincethe percentage of modulation of only one of the frequencies f1, f2varies tio -.91 t e restiszay the i embodiment the percentage modulationof both these frequencies vary in opposite senses, obviously givinggreater accuracy in the definition of the directional axis.

If at the receiving station there are employed acoustical methods forcomparing currents at frequencies f1 and f2, these frequencies shouldclearly be audible, but if one utilises other methods (for exampleoptical or electrical) it is clear that it need not necessarily be so,as in such cases these frequencies may be for example above the audiblerange.

What I claim is:

1. Radio position determining apparatus comprising high frequencytransmitting apparatus, a pair of antennas connected to said transmittng apparatus, said antennas being positioned in relatively closeproximity to each other, low frequency oscillation generating apparatusfor producing a pair of low frequency oscillations, modulator apparatusfor selectively modulating said high frequency transmitting apparatus inaccordance with said low frequency oscillations, and phase adjustingapparatus connected to said high frequency transmitting apparatus foradjusting the phase of the Waves radiated by said antennas so that afield is radiated having an axis along which the resultant field ismodulated by the two low frequency, oscillations equally and on theopposite sides of which axis the resultant field is modulated todifferent degrees by each of said low frequencies.

2. Radio position determining apparatus comprising a first transmitter,a first antenna connected to said first transmitter, a secondtransmitter, a second antenna connected to said second transmitter andpositioned in relatively close proximity to said first antenna, a highfrequency oscillation generator connected to said first and said secondtransmitters, oscillator means for producing a pair of modulationfrequencies, a pair of modulators connected between said high frequencyoscillation generator and said second transmitter for modulating saidsecond transmitter in accordance with said pair of modulationfrequencies, and apparatus for adjusting the phase of the waves radiatedby said first and said second antennas so that a field is radiatedhaving an axis along which the resultant field is modulated by the twomodulation frequencies equally, the percentage modulation'of saidresultant field by one of said modulation frequencies increasing and thepercentage modulation by the other of said modulation frequenciesdecreasing on opposite sides of said axis.

3. Apparatus as set forth in claim 1 further comprising ,a receivingapparatus carried by a mobile craft remote from said high-frequencytransmitting apparatus and having an amplifier and detector, a pair offilters adjusted to select the pair of low frequency oscillations withwhich the aforesaid resultant field is modulated and means connected tothe output of said filters for indicating the amplitudes of said lowfrequency oscillations whereby the operator of said mobile craft maydetermine the side of the aforesaid axis the craft is located.

4. Radio position determining apparatus as set forth in claim 2 furthercomprisinga radio receiving apparatus carried by a mobile craft remotefrom said transmitters and responsive to the signal transmitted thereby,said receiving apparatus comprising an amplifier, a detector, a pair offilters tuned to select said modulation frequencies and apparatusresponsive to the two modulation frequencies to indicate the amplitudesthereof whereby the operator of the mobile craft may determine the sideof the aforesaid axis the craft is located.

5. Radio apparatus for direction finding comprising a first transmitter,a first antenna connected to said first transmitter, a secondtransmitter, a second antenna connected to said second transmitter anddisposed relatively near said first antenna; a high frequencyoscillation generator connected to said first and to said secondtransmitters, oscillators for supplying a pair of modulationfrequencies, a pair of modulators disposed between said highfrequencyoscillation generator and said second transmitter for modulatingsaidsecond transmitter with said pair of modulation frequencies; a firstphase shifter connected between said high frequency oscillationgenerator and the first of said pair of modulators, and a second phaseshifter connected between said high frequency oscillation generator andthe second of said pair of modulators, so that a field is radiatedhaving an axis along which the resulting field is modulated by the twomodulation frequencies, the amount of modulation of said field resultingfrom one of said frequencies increasing and the amount of modulationfrom the other of said frequencies decreasing on opposite sides of saidaxis. t

6. Radio apparatus for direction finding comprising a first transmitter,a first antenna connected to said first transmitter, a secondtransmitter, a second antenna connected to said second transmitter anddisposed relatively near said first antenna; a high frequencyoscillation generator connected to said first and to said secondtransmitter; oscillators for supplying a pair of modulation frequencies,a pair of modulators disposed between said high frequency oscillationgenerator and said second transmitter for modulating said secondtransmitter with said pair of modulation frequencies; means forsuppressing the carrier of said second transmitter, a first phaseshifter connected between said high frequency oscillation generator andthe first of said pair of modulators, and a second phase shifterconnected between said high frequency oscillation generator and thesecond of said pair of modulators, so that a field is radiated having anaxis along which the resulting field is modulated by the two modulationfrequencies, the amount of modulation of said field resulting from oneof said frequencies increasing and the amount of modulation from theother of said frequencies decreasing on opposite side of said axis.

. JOSEPH AICARDI.

REFERENCES CITED The following references are of record in the file ofthis patent:

